Retention of asbestos fibers in the human body

Our plain-English summary of Retention of asbestos fibers in the human body, by A. Tossavainen, A. Karjalainen, P.J. Karhunen (Environmental Health Perspectives, 1994).

The study

• Authors: A. Tossavainen, A. Karjalainen, P.J. Karhunen
• Journal: Environmental Health Perspectives
• Published: 1994;102 Suppl 5(Suppl 5):253-5
• Cited by: 34 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The number, type, and size of retained asbestos fibers were measured by scanning electron microscopy (SEM) in lung tissues of 10 workers who had died from lung cancer or mesothelioma. The levels were 190-3000 x 10(6) fibers/g of dry tissue in three crocidolite sprayers, 6-39 x 10(6) fibers/g of dry tissue in two asbestos product workers and 13-280 x 10(6) fibers/g of dry tissue in five insulators exposed to anthophyllite. The duration of past exposure corresponding to the limit of 1 million fibers/g of dry tissue was 1 to 2 days in spraying, 3 to 10 days at the production plant and 1 to 4 months in insulation work. No long-term clearance of amphibole fibers, > 5 microns in length, could be demonstrated. In one of the sprayers the fiber concentrations of lung parenchyma, visceral and parietal pleura, hilar lymph nodes, and kidney cortex were orders of magnitude higher than in a series of unselected autopsies. The size and aspect ratio of crocidolite fibers in various tissues were similar, indicating that the translocation processes are rather unselective in respect to fiber dimensions.

In plain English

This Finnish study measured asbestos fibers retained in the bodies of 10 men, aged 44 to 69 at diagnosis, who had been heavily exposed to asbestos and had lung cancer or mesothelioma. Tissue was taken in 1988 to 1992 during surgery or autopsy and examined by scanning electron microscopy. Lung levels were 190 to 3000 million fibers per gram of dry tissue in three crocidolite sprayers, 6 to 39 million in two asbestos product workers, and 13 to 280 million in five insulators. The product workers and insulators were exposed mainly to anthophyllite. The authors estimated that about 1 to 2 days of spraying, 3 to 10 days of raw-material mixing, or 1 to 4 months of pipe insulation work corresponded to 1 million fibers per gram measured years later. In one sprayer, crocidolite was found in the pleura, in hilar lymph nodes (7400 million per gram) and in kidney cortex (30 million per gram, orders of magnitude above unselected autopsies). Fiber sizes were similar across these tissues. The authors concluded that no clearance of long amphibole fibers could be demonstrated. They noted that their calculations involved considerable and unquantifiable uncertainty.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Case series measuring retained asbestos fibers in tissues by scanning electron microscopy, with a comparison series of 10 unselected autopsies
• Who was studied: 10 men in Finland (3 crocidolite sprayers, 2 asbestos product workers, 5 insulators), aged 44 to 69 at diagnosis, with lung cancer (some with asbestosis), peritoneal mesothelioma (2 sprayers) or pleural mesothelioma (1 insulator); tissue samples taken 1988 to 1992 at surgery or autopsy. A comparison group of 10 autopsied cases came from an unselected series of sudden Finnish male deaths.
• Exposure: Heavy occupational exposure to crocidolite (sprayers) or anthophyllite (asbestos product workers and insulators), verified by lung dust analyses and personal interviews
• Main results:
  • Lung tissue levels were 190 to 3000 million fibers per gram of dry tissue in the three crocidolite sprayers, 6 to 39 million in the two asbestos product workers, and 13 to 280 million in the five insulators
  • About 1 to 2 days of crocidolite spraying corresponded to 1 million fibers per gram measured several years after exposure ended
  • For mixers of raw materials at the production plant the corresponding figure was 3 to 10 days
  • For pipe insulators the corresponding figure was 1 to 4 months
  • In one asbestos sprayer, the crocidolite level was highest in hilar lymph nodes (7400 million per gram), followed by lung parenchyma (190), visceral pleura (145) and parietal pleura (12)
  • In the same sprayer the kidney cortex contained 30 million fibers per gram, which the authors described as orders of magnitude greater than levels in the 10 unselected autopsies
  • In the unselected autopsy series, lung levels ranged from less than 0.1 to 1.6 million fibers per gram (mean 0.5 million), at or below the 1 million per gram limit the laboratory uses to distinguish occupationally exposed persons
  • In the unselected autopsy series, lymph node levels ranged from 5 to 81 million fibers per gram (mean 21 million), about 40-fold higher than in their lungs, a ratio close to that in the exposed sprayer
  • Median crocidolite fiber dimensions were 2.0 to 3.0 micrometers in length, 0.12 to 0.13 micrometers in diameter and 17 to 24 for aspect ratio, with no obvious difference between tissues
  • Fibers longer than 5 micrometers made up 20% of crocidolite fibers and about 50% of anthophyllite fibers
  • The estimated exposure data for the sprayers and product workers were consistent with a clearance half-time of 10 years or more
  • The authors interpreted the similar fiber sizes in tissues outside the lung as indicating that transport of fibers to those tissues was rather unselective with respect to fiber dimensions
• The authors' conclusion: The authors concluded that no clearance of long amphibole fibers from the alveolar region of the lungs was demonstrable by their kinetic calculations
• Limitations the authors state:
  • The calculation of retained fibers depends on many parameters subject to considerable and unquantifiable uncertainty
  • The original fiber levels in the lungs were not known
  • The exposure-to-lung-level calculations assumed amphibole clearance was negligible and did not account for time since exposure
  • Inhalation rate, deposition and lung weight were roughly estimated from published data

Topics

The National Library of Medicine indexes this study under subjects our site covers: Anthophyllite, Crocidolite.

Medical terms in this study, explained in our Lexicon: Scanning Electron Microscopy (SEM), Lung Cancer, Mesothelioma, Crocidolite, Insulator, Anthophyllite, Amphibole Group, Parenchyma.

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